The fabrication of a semiconductor device involves a plurality of discrete and complex processes. One such process may utilize an ion beam, which may be extracted from an ion source. In an ion source, a feed gas is energized to form ions. Those ions are then extracted from the ion source through an extraction aperture disposed on an extraction plate. The ions are attracted to a workpiece that is scanned relative to the extraction aperture. These ions may be used to implant a dopant in the workpiece, etch the workpiece, deposit a coating on the workpiece or amorphize the workpiece.
To attract the ions, the extraction plate and the workpiece may be biased at different voltages. For example, if the workpiece is biased at a voltage that is more negative than the extraction plate, positive ions from within the ion source will be attracted to the workpiece.
In many embodiments, the extraction plate is formed of an electrically conductive material, such as a metal. Similarly, the workpiece is disposed on a second electrically conductive material, commonly referred to as a platen. Another electrically conductive element commonly referred to as a shield or halo, may be configured so that it surrounds the workpiece to protect the neighboring area from the negative effects of ion beam strikes, such as particles and metals being deposited onto the workpiece. The shield or halo also provides a very similar electrical potential surface and current path as the workpiece, in order for the workpiece to be processed uniformly.
One issue associated with this configuration is the generation of particles, especially particles that ultimately become disposed on the workpiece. Specifically, as the ions exit the ion source, the energy of the ions may cause particles to be emitted by the extraction plate. Additionally, the ions striking the shield may also cause particles to be emitted by the shield. These particles may become disposed on the workpiece and may degrade the performance of the workpiece.
Therefore, it would be beneficial if there were a system for implanting ions into a workpiece that reduced the amount of particles that are generated. Further, it would be advantageous if the operating parameters of the system were not negatively affected.